The present invention is related to MEMS devices and in particular to hinges and electrical connections for MEMS devices. More particularly, the invention is related to hinge and electrical connection shapes, characteristics and/or materials for MEMS device, in particular micromirror or other electrostatically deflectable micromechanical elements.
There are many MEMS devices in which a movable element is connected to a rigid substrate through flexible hinges. These hinges allow the movable element to move. The most commonly used MEMS materials are single crystal silicon, polysilicon, and silicon nitr. All of these are good MEMS materials because they deform nearly perfectly elastically, and also the first two conduct electricity, which enables a variety of electrostatic actuators, fabricated for example in the MUMPS or SUMMIT processes.
These materials do not solve all MEMS device requirements however, because they are difficult to fabricate. Single crystal silicon must be cut out of a wafer. Polysilicon requires high temperature deposition, and silicon nitride does not conduct. A high deposition temperature step is undesirable because it can disturb other films deposited at lower temperatures, e.g. aluminum. Silicon nitride does not conduct and thus is not sufficient alone.
A common approach in MEMS devices is to use an insulating mechanical layer in a laminate with an additional metal layer provided to conduct electricity. However, metallic layers often do not deform elastically once their rather low strain limits are exceeded. As a result, fatigue, fracture and creep sometimes results after repeated actuation.
What are needed are novel materials and designs for MEMS devices that allow for electrical conductivity to a MEMS movable element as well as elastic deformation of such a movable element without fatigue or other damage modes.